{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,11,2]],"date-time":"2025-11-02T20:05:12Z","timestamp":1762113912965,"version":"build-2065373602"},"reference-count":22,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2022,5,3]],"date-time":"2022-05-03T00:00:00Z","timestamp":1651536000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Jilin Province Science and technology resources open sharing service platform and scientific research condition guarantee project","award":["20191004022TC","201506230147C","XJJLG-2018-03"],"award-info":[{"award-number":["20191004022TC","201506230147C","XJJLG-2018-03"]}]},{"name":"JJilin Science and technology development plan project","award":["20191004022TC","201506230147C","XJJLG-2018-03"],"award-info":[{"award-number":["20191004022TC","201506230147C","XJJLG-2018-03"]}]},{"name":"Youth Innovation Fund Project of Changchun University of Science and Technology","award":["20191004022TC","201506230147C","XJJLG-2018-03"],"award-info":[{"award-number":["20191004022TC","201506230147C","XJJLG-2018-03"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>During terahertz (THz) non-destructive testing (NDT), multiple echoes from the sample interface reflection signals are mixed with the detection signals, resulting in signal distortion and affecting the accuracy of the THz NDT results. Combined with the frequency property of multiple echoes, an improved wavelet multi-scale analysis is put forth in this paper to correct multiple echoes, allowing the maximum retention of detailed signal information in contrast with the existing echo correction methods. The results showed that the improved wavelet multi-scale analysis enhanced the continuity and smoothness of the image at least twice in testing adhesive layer thickness, prevented missing judgments and misjudgments in identifying characteristic defects, and ensured accurate detection results. Hence, it is of great significance for evaluating the THz NDT results.<\/jats:p>","DOI":"10.3390\/s22093477","type":"journal-article","created":{"date-parts":[[2022,5,3]],"date-time":"2022-05-03T08:26:35Z","timestamp":1651566395000},"page":"3477","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":5,"title":["Terahertz Multiple Echoes Correction and Non-Destructive Testing Based on Improved Wavelet Multi-Scale Analysis"],"prefix":"10.3390","volume":"22","author":[{"given":"Weihua","family":"Xiong","sequence":"first","affiliation":[{"name":"School of Optoelectronics Engineering, Changchun University of Science and Technology, Changchun 130000, China"},{"name":"Key Laboratory of Optoelectronic Measurement and Control and Optical Information Transmission Technology, Ministry of Education, School of Optoelectronic Engineering, Changchun University of Science and Technology, Changchun 130022, China"},{"name":"Zhongshan Research Institute, Changchun University of Science and Technology, Zhongshan 528403, China"}]},{"given":"Lijuan","family":"Li","sequence":"additional","affiliation":[{"name":"School of Optoelectronics Engineering, Changchun University of Science and Technology, Changchun 130000, China"},{"name":"Key Laboratory of Optoelectronic Measurement and Control and Optical Information Transmission Technology, Ministry of Education, School of Optoelectronic Engineering, Changchun University of Science and Technology, Changchun 130022, China"},{"name":"Zhongshan Research Institute, Changchun University of Science and Technology, Zhongshan 528403, China"}]},{"given":"Jiaojiao","family":"Ren","sequence":"additional","affiliation":[{"name":"School of Optoelectronics Engineering, Changchun University of Science and Technology, Changchun 130000, China"},{"name":"Key Laboratory of Optoelectronic Measurement and Control and Optical Information Transmission Technology, Ministry of Education, School of Optoelectronic Engineering, Changchun University of Science and Technology, Changchun 130022, China"},{"name":"Zhongshan Research Institute, Changchun University of Science and Technology, Zhongshan 528403, China"}]},{"given":"Jian","family":"Gu","sequence":"additional","affiliation":[{"name":"School of Optoelectronics Engineering, Changchun University of Science and Technology, Changchun 130000, China"},{"name":"Key Laboratory of Optoelectronic Measurement and Control and Optical Information Transmission Technology, Ministry of Education, School of Optoelectronic Engineering, Changchun University of Science and Technology, Changchun 130022, China"},{"name":"Zhongshan Research Institute, Changchun University of Science and Technology, Zhongshan 528403, China"}]},{"given":"Dandan","family":"Zhang","sequence":"additional","affiliation":[{"name":"School of Optoelectronics Engineering, Changchun University of Science and Technology, Changchun 130000, China"},{"name":"Key Laboratory of Optoelectronic Measurement and Control and Optical Information Transmission Technology, Ministry of Education, School of Optoelectronic Engineering, Changchun University of Science and Technology, Changchun 130022, China"},{"name":"Zhongshan Research Institute, Changchun University of Science and Technology, Zhongshan 528403, China"}]},{"given":"Junwen","family":"Xue","sequence":"additional","affiliation":[{"name":"School of Optoelectronics Engineering, Changchun University of Science and Technology, Changchun 130000, China"},{"name":"Key Laboratory of Optoelectronic Measurement and Control and Optical Information Transmission Technology, Ministry of Education, School of Optoelectronic Engineering, Changchun University of Science and Technology, Changchun 130022, China"},{"name":"Zhongshan Research Institute, Changchun University of Science and Technology, Zhongshan 528403, China"}]}],"member":"1968","published-online":{"date-parts":[[2022,5,3]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"265","DOI":"10.3724\/SP.J.1010.2013.00265","article-title":"The removal of echo signals in terahertz time-domain spectroscopy","volume":"32","author":"Wang","year":"2013","journal-title":"J. Infr. Millim. Waves"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"325101","DOI":"10.1088\/1361-6463\/aad0ca","article-title":"Interference elimination in terahertz imaging based on inverse image processing","volume":"51","author":"Wang","year":"2018","journal-title":"J. Phys. D Appl. Phys."},{"key":"ref_3","first-page":"451","article-title":"Research on bonding defect detection method of aerospace composites based on terahertz image","volume":"39","author":"Pan","year":"2018","journal-title":"J. Metrol."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"647","DOI":"10.1541\/ieejpes.135.647","article-title":"Nondestructive testing using terahertz waves","volume":"135","author":"Fukuchi","year":"2015","journal-title":"IEEJ Trans. Power Energy"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"2126","DOI":"10.1109\/TDEI.2016.7556487","article-title":"Research of nondestructive methods to test defects hidden within composite insulators based on THz time-domain spectroscopy technology","volume":"23","author":"Cheng","year":"2016","journal-title":"IEEE Trans. Dielectr. Electr. Insul."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"112624","DOI":"10.1016\/j.compstruct.2020.112624","article-title":"Nondestructive testing of bonding defects in multilayered ceramic matrix composites using THz time domain spectroscopy and imaging","volume":"251","author":"Zhang","year":"2020","journal-title":"Compos. Struct."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"841","DOI":"10.1016\/j.mejo.2008.01.001","article-title":"Techniques for cancellation of interfering multiple reflections in terahertz time-domain measurements","volume":"39","author":"Hirsch","year":"2008","journal-title":"Microelectron. J."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"291","DOI":"10.1016\/j.optcom.2007.08.042","article-title":"A method for removing etalon oscillations from THz time-domain spectra","volume":"280","author":"Naftaly","year":"2007","journal-title":"Opt. Commun."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"443","DOI":"10.1109\/TTHZ.2020.3001508","article-title":"A reliable method for removing Fabry-P\u00e9rot effect in material characterization with terahertz time-domain spectroscopy","volume":"10","author":"Liu","year":"2020","journal-title":"IEEE Trans. Terahertz Sci. Technol."},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"Yang, Y., Dal Forno, S., and Battiato, M. (2021). Removal of Spectral Distortion Due to Echo for Ultrashort THz Pulses Propagating Through Multilayer Structures with Thick Substrate. J. Infrared Millim. Terahertz Waves.","DOI":"10.1007\/s10762-021-00815-5"},{"key":"ref_11","unstructured":"Wang, L., Liu, Y., Wang, Y., and Zhao, Z. (2012, January 5\u20138). Novel band-notch monopole ultra-wideband antenna with external load. Proceedings of the 2012 International Conference on Microwave and Millimeter Wave Technology (ICMMT), Shenzhen, China."},{"key":"ref_12","unstructured":"Liu, H., Zhang, Z., and Zhang, C. (2017, January 28\u201330). Enhancement of Sensitivity for Bioanalysis by Liquid Chromatography-Electrospray Mass Spectrometry with Trifluoroacetic Acid in Mobile Phase Using a Suppressor. Proceedings of the 2017 International Conference on Optical Instruments and Technology: IRMMW-THz Technologies and Their Applications, Beijing, China."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"77","DOI":"10.1063\/1.2810419","article-title":"Optical waves in layered media","volume":"43","author":"Yeh","year":"1990","journal-title":"Phys. Today"},{"key":"ref_14","first-page":"3169","article-title":"Joint time-frequency analysis for removing the spectral interference of terahertz","volume":"30","author":"Sun","year":"2010","journal-title":"Spectrosc. Spectr. Anal."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"19901","DOI":"10.1364\/OE.394177","article-title":"THz imaging technique for nondestructive analysis of debonding defects in ceramic matrix composites based on multiple echoes and feature fusion","volume":"28","author":"Zhang","year":"2020","journal-title":"Opt. Express"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"36","DOI":"10.1016\/j.infrared.2019.02.003","article-title":"Terahertz nondestructive imaging for foreign object detection in glass fibre-reinforced polymer composite panels","volume":"98","author":"Wang","year":"2019","journal-title":"Infrared Phys. Technol."},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Charbon, E. (2014, January 2\u20135). Introduction to time-of-flight imaging. Proceedings of the SENSORS, 2014 IEEE, Valencia, Spain.","DOI":"10.1109\/ICSENS.2014.6985072"},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Giacomantone, J., Violini, M.L., and Lorenti, L. (2017). Background Subtraction for Time of Flight Imaging. J. Comput. Sci. Technol.","DOI":"10.24215\/16666038.17.e18"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"3863","DOI":"10.1364\/OL.34.003863","article-title":"Compressed sensing pulse-echo mode terahertz reflectance tomography","volume":"34","author":"Jin","year":"2009","journal-title":"Opt. Lett."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"601","DOI":"10.1111\/j.1365-2966.2008.13292.x","article-title":"Timeline analysis and wavelet multiscale analysis of the AKARI All-Sky Survey at 90 \u03bcm","volume":"387","author":"Wang","year":"2008","journal-title":"Mon. Not. R. Astron. Soc."},{"key":"ref_21","doi-asserted-by":"crossref","unstructured":"Khani, M.E., and Arbab, M.H. (2022). Translation-Invariant Zero-Phase Wavelet Methods for Feature Extraction in Terahertz Time-Domain Spectroscopy. Sensors, 22.","DOI":"10.3390\/s22062305"},{"key":"ref_22","doi-asserted-by":"crossref","unstructured":"Zhang, J., Ren, J., Li, L., Gu, J., Zhang, D., and Zhou, T. (2021). Defect Identification of Layered Adhesive Structures based on Dynamic Time Warping and Simulation Analysis. Infrared Phys. Technol., 120.","DOI":"10.1016\/j.infrared.2021.103943"}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/22\/9\/3477\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T23:05:43Z","timestamp":1760137543000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/22\/9\/3477"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2022,5,3]]},"references-count":22,"journal-issue":{"issue":"9","published-online":{"date-parts":[[2022,5]]}},"alternative-id":["s22093477"],"URL":"https:\/\/doi.org\/10.3390\/s22093477","relation":{},"ISSN":["1424-8220"],"issn-type":[{"type":"electronic","value":"1424-8220"}],"subject":[],"published":{"date-parts":[[2022,5,3]]}}}